fix: use documented swapon show columns

traffic_core/src/swap/runtime.rs

@@ -11,17 +11,17 @@ use std::os::unix::fs::PermissionsExt;
 
 use super::model::ActiveSwap;
 
+fn swapon_show_args() -> [&'static str; 4] {
+    [
+        "--show=NAME,TYPE,SIZE,PRIO",
+        "--bytes",
+        "--raw",
+        "--noheadings",
+    ]
+}
+
 pub(super) fn read_active_swaps() -> anyhow::Result<Vec<ActiveSwap>> {
-    let out = Command::new("swapon")
-        .args([
-            "--show",
-            "--bytes",
-            "--raw",
-            "--noheadings",
-            "--output",
-            "NAME,TYPE,SIZE,PRIO",
-        ])
-        .output()?;
+    let out = Command::new("swapon").args(swapon_show_args()).output()?;
     if !out.status.success() {
         anyhow::bail!(
             "swapon --show failed: {}",
@@ -111,6 +111,20 @@ pub(super) fn run(program: &str, args: &[&str]) -> anyhow::Result<()> {
 #[cfg(test)]
 mod tests {
     use super::*;
+
+    #[test]
+    fn swapon_uses_the_documented_show_columns_form() {
+        assert_eq!(
+            swapon_show_args(),
+            [
+                "--show=NAME,TYPE,SIZE,PRIO",
+                "--bytes",
+                "--raw",
+                "--noheadings"
+            ]
+        );
+    }
+
     #[test]
     fn parse_swapon_empty() {
         let got = parse_swapon_output("").expect("parse");